This invention is related to porous substrates sintered from aluminide powders and their alloys. In particular, nickel, titanium, and rare earth metal aluminides are structured with the addition and/or substitution of other metal components.
Processes for making porous aluminide substrates from metal powders have been burdened by the presence of an oxide layer, making sintering operations difficult to impossible. The present invention introduces an aluminide component in a structure in cooperation with various alloy combinations. These combinations are useful as wear and chemically resistant, mechanically stable substrates for use in harsh environments, such as exhaust and corrosive pathways. Methods of use for aluminide structures may be advantageously employed in filtering operations, e.g. diesel particulate filters or molten metal filters, or as catalyst supports for catalytic converters or DeNOx applications. Consequently, these structures can be placed as catalyzed structures in the exhaust path of power plants and internal combustion engines.
Equally beneficial uses may be found for the formed product as a structural material. For example, when extruded as a honeycomb structure the aluminide material is light weight with abundant lateral and vertical mechanical strength, providing a light weight structural intermediary.
U.S. Pat. No. 4,758,272 provided break through technology wherein it was disclosed that iron aluminum alloy powders could be successfully sintered, the disclosure of which is hereby incorporated by reference as filed. Therein, an oxide gettering process was employed thus enabling sintering of the alloy.
In copending U.S. patent application Ser. No. 219,986, filed July 15, 1988, it is disclosed that gettering such material is an option, and that sintering in an inert environment is operable as well. The disclosure therein is hereby incorporated by reference as filed. Both disclosures relate to the iron aluminum alloy system.
Aluminides of other metal and/or metal alloy systems have been as stubbornly resistant to sintering operations as was their cousin, iron aluminum. Various aluminide alloys could find useful employ as a porous structure if their alloyed powder starting materials were susceptible to sintering operations. Additionally, the ability to form structures of the aluminide material from a wet batch provides economies of production heretofore unseen in the workings of these materials.
The invention, herein disclosed, enables the use of powdered aluminides in wet batch forming operations, that have subsequently been successfully sintered into porous formed structures. The process for sintering the aluminides may be a one step operation or extended to multiple steps.